Euston-Brown, D., Rathogwa, N & Richardson ... - DWA Home Page

Contents
1. Executive Summary..................................................................................................................................................................... 7
2. Introduction .................................................................................................................................................................................. 8
2.1 Terms of Reference ............................................................................................................................................................. 8
2.2 Key questions ........................................................................................................................................................................ 9
3. Methodology............................................................................................................................................................................... 10
4. Findings ....................................................................................................................................................................................... 11
4.1 Overview of Sweet Grassveld and Mesic Savanna ecosystems............................................................................... 11
4.1.1 Description of vegetation.................................................................................................................................... 11
4.1.2 Description of ecosystem functioning .............................................................................................................. 11
4.2 Overview of Chromolaena and Lantana and other invasive weeds in these ecosystems..................................... 14
4.2.1 How do Chromolaena and Lantana establish and persist in these particular Savanna systems?......... 14
4.2.2 Biology and ecology Chromolaena odorata .................................................................................................... 16
4.2.3 Biology and ecology Lantana camara ............................................................................................................. 18
4.2.4 Overview of other weeds that are problematic in this system .................................................................... 19
4.2.5 Description and assessment of the invasion problem ................................................................................... 21
4.3 Summary of insights on the effectiveness of clearing methods................................................................................. 22
4.3.1 The different control options that can be used. .............................................................................................. 22
4.3.1.1 Biological control ................................................................................................................................... 22
4.3.1.1a) For chromolaena.................................................................................................................. 22
4.3.1.1b) For lantana ............................................................................................................................ 23
4.3.1.2 Mechanical control – hand pulling, slashing, mowing, bull dozers and browsing/grazing....... 24
4.3.1.2a) Handpulling .......................................................................................................................... 24
4.3.1.2b) Slashing................................................................................................................................. 25
4.3.1.2c) Mowing.................................................................................................................................. 26
4.3.1.2d) Bulldozing.............................................................................................................................. 27
4.3.1.2e) Browsing/Grazing ................................................................................................................ 27
4.3.1.3 Herbicidal control – Foliar spray, cut & treat and aerial spraying................................................. 28
4.3.1.3a) Foliar spray............................................................................................................................ 30
4.3.1.3b) Cut-and-treat-stump............................................................................................................ 32
4.3.1.3c) Aerial spraying ..................................................................................................................... 33
4.3.1.4 Cultural control – mulching, competition and fire ............................................................................ 33
4.3.1.4a) Mulching................................................................................................................................ 33
4.3.1.4b) Competition........................................................................................................................... 33
4.3.1.4c) Fire.......................................................................................................................................... 34
4.3.2 The different situations or conditions in terms of habitat type and land use............................... 35
4.3.2.1 Brief description of each unit in terms of habitat and clearing options. ...................................... 36
4.3.2.1a) Flat riparian savanna........................................................................................................... 36
4.3.2.1b) Steep riparian forest............................................................................................................ 37
4.3.2.1c) Lowveld Riparian forest...................................................................................................... 37
4.3.2.1d) Open savanna – lowveld..................................................................................................... 37
4.3.2.1e) Open savanna – lower and mid slopes ............................................................................ 37
4.3.2.1f ) Mixed Bushveld on rocky hillsides ................................................................................... 37
4.3.2.1g) Forest ..................................................................................................................................... 38
4.3.3 The different densities and cover of chromolaena and lantana ................................................................. 38
4.3.4 The influence of season and climate on the choice and timing of control method.................................. 39